1.

passenger train takes 1 hour less when its speed is increased by 15 km per hour. Then its usual speed for a journey of 300 kilometre. Find the usual speed of the train.​

Answer»

Step-by-step ⇒ Let the usual speed of the train be xkm/hr

⇒ Distance COVERED in the journey=150km

⇒ Time TAKEN by the train with usual speed =

x

150

hr

⇒ New speed of train =(x+5)km/hr

⇒ Time taken by the train after increasing the speed =

x+5

150

hr

x

150

−

x+1

150

=1

⇒ 150(

x

1

−

x+5

1

)=1

⇒ 150(

x(x+5)

x+5−x

)=1

⇒ 150(5)=x(x+5)

⇒ 750=x

2

+5x

⇒ x

2

+5x−750=0

⇒ x

2

+30x−25x−750=0

⇒ x(x+30)−25(x+30)=0

⇒ (x+30)(x−25)=0

⇒ x+30=0 and x−25=0

⇒ x=−30 and x=25

Speed cannot be negative.

∴ The usual speed of the train is 25km/hr


Discussion

No Comment Found

Related InterviewSolutions